A quick check would be to pull the ignition wires, ONE AT A TIME, off the coil terminals.....if you find carbon/corrosion on the coil terminal(remember one at a time so you don't get the wires mixed up), you can clean the terminal, but you will need new wires.....
So probably, your best move is a COMPLETE tuneup....use good wires(not cheapo's), use OEM plugs and check gap, replace air and fuel filter and PCV valve, and if the misfire is still there , you will have to do a coil output test on each coil terminal, with a spark tester....